1. Field
The field of the embodiments generally relates to improved techniques and architectures for modifying the physical design and realization of integrated circuits, and more specifically to an architecture of spare wiring structures for improved engineering change orders.
2. Related Art
Integrated circuit design typically involves a series of well-defined steps using a sequence of electronic-design-automation (EDA) or computer aided design (CAD) tools. In a first step, the required functionality of the design is typically specified using a hardware description language (HDL) or by drawing a schematic with a graphical entry tool. Regardless of the mechanism used to specify the design, the design is converted to a netlist of logic elements through a step known as synthesis by an EDA software tool. The synthesis tool specifies the design as a netlist of circuit elements in a way that optimizes the design as specified using user-supplied constraints. These constraints may include optimizing for a desired operating speed, implementation area, or power-efficiency, etc. Given that the post-synthesis netlist meets the desired optimization requirements, an EDA tool then derives a silicon layout of the design netlist through a series of steps called placement, clock-tree synthesis, timing optimization, and routing. The outcome of the layout process is the physical design of the integrated circuit.
After the physical design of the integrated circuit has been generated through the layout design-automation tool, it is used to build a photomask set with each photomask being used for a separate photolithographic step during manufacture of the integrated circuit. The costs associated with the production of each photomask and the set as a whole is a significant part of the total cost of fabricating an integrated circuit.
If there are design errors or specification changes found after the photomask set has been manufactured, one or more of the photomasks must be redesigned and remanufactured. Changes are first made to the netlist and physical design before the relevant replacement photomasks are manufactured. The process of modifying or updating a design in such a way is referred to as an engineering change, an engineering change order, or in short as an ECO. To reduce costs, it is typically desirable to perform engineering change orders such that the desired change in design functionality or the physical realization is achieved while altering as few photomasks as possible, especially those photomasks that are more expensive to manufacture.
If an engineering change requires the refabrication of too many photomasks, the increased manufacturing costs, schedule delays, and risks associated with the engineering change may warrant a full revision, in which case the entire photomask set must be redesigned and remanufactured. The feasibility of an engineering change is a determination of whether or not an engineering change is possible without the need for modifying all photomasks, otherwise known as a full revision.